There are many known forms of mining or cutting bits having conical heads and cylindrical shanks provided with various forms of means for mounting the bit in holders or mounts which allows for rotation of the bit therein to provide an even distribution of wear. Examples of these may be found in U.S. Pat. Nos. 3,512,838 issued May 19, 1970; 3,519,309 issued July 7, 1970 and 1,550,669 issued Aug. 25, 1925. Recently it has become popular to provide a wear sleeve between the stem or shank of the bit and the socket of the mount to, among other things, prevent wear on the shank of the bit while also retaining the bit in the socket. This type of bit arrangement is disclosed in my U.S. Pat. No. 4,201,421 issued May 1, 1980, which has been found immanently satisfactory to the trade.
In certain applications, particularly high speed operation, it is desirable to mount the bit so as to provide added insurance that the bit won't be prematurely ejected from the mount presenting a dangerous situation, while allowing the use of the wear sleeve as described in my aforenoted patent.